Polytetrafluoroethylene fiber

A PTFE fiber that is adapted to be sewn at high speeds. The fiber has a toughness greater than about 0.36 grams per denier (g/d). A range for the toughness is from about 0.36 to about 1.01 g/d, with a preferred range being from about 0.50 to about 0.80 g/d. The toughness of the inventive PTFE fiber is most preferably about 0.60 g/d. The inventive fiber has a peak engineering stress greater than about 1.6 g/d and a break strain greater than about 15.5 percent. A preferred range for the peak engineering stress is from about 3.0 g/d to about 5.0 g/d, and a preferred range for the break strain is from about 20 percent to about 50 percent. Most preferably, the peak engineering stress is about 4.4 g/d, and the break strain is about 24 percent. In another aspect, this invention provides a process for making a fiber that involves providing a PTFE fiber and heating the PTFE fiber to a temperature of from about 300 DEG C. to about 500 DEG C., while overfeeding the PTFE fiber at an overfeed of up to about 70 percent. A preferred range for the temperature is from about 350 DEG C. to about 450 DEG C., and a preferred range for the overfeed in the overfeeding step is from about 10 percent to about 20 percent. Most preferably, the temperature in the heating step is about 400 DEG C. and the overfeed in the overfeeding step is about 15 percent. The PTFE fiber may be used as a filament for an improved dental floss, and is also suited for an improved bearing material.